Assignment 7 Sheqi

Assignment7 Sheqi.out

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+Assignment 7  Sheqi Zhang
+
+1. Explain the difference between ++*p, *p++ and *++p, if there is any. 
+Answer:
+++*p increments the value at location p points to, then evaluates to incremented value.
+*p++ evaluates the value at location p points to, then advances p.
+*++p increments the value of p, then evaluate the location ++p points to.
+
+2. Is the left to right or right to left order guaranteed for operator precedence?
+Answer:
+In most situations, the left to right order is guarenteed, while for operators like "+=","-=", the order is right to left.
+
+3. What is the advantage of using pointers?
+Answer:
+The pointer provide a way for functions to modify their calling argument, and it supports the dynamic memory allocation. It's more effecient comparing with arrays.
+
+4. 
+ 4.1 "abc" <br>
+	char
+ 4.2 "xyz"[1] - ’y’ <br>
+	Invalid. "xyz"[1] is an array, while 'y' is character;
+ 4.3 ’\0’ == 0 <br>
+	boolean. It is judging if it's wrong.
+ 4.4 *a <br>
+	pointer. Because there is a "*" in front of "a".
+ 4.5 &a[0] <br>
+	pointer or array.
+	It can be the array in the scanf function, it can also be the pointer of the variable a[0].
+ 4.6 *p <br>
+	pointer. Because there is a "*" in front of "p".
+ 4.7 &p <br>
+	pointer or variable.
+	Because there is a "&", it may be a pointer. While it can also be a variable in the scanf function.
+ 4.8 *++argv <br>
+	pointer. Because there is a "*".
+ 4.9 &main <br>
+	Because there is a "&", it may be a pointer. While it can also be a variable in the scanf function.
+ 4.10 sizeof(str) <br>
+	Integer. The value is the length of str. 3?
+
+
+

Final Project Proposal

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+Proposal of Final Project  Sheqi
+
+My plan is to write a program that can calculate the frequency of the words appearing in a document.
+
+I want to do this because I think it's useful, and I believe the most important characteristic of computer programming is useful. In addition, I can almost handle it with the things I have learend in the summer program.
+
+Steps:
+1. Open document 1 and read it, and judge if it opens successfully at the same time.
+2. If open successfully, as well as not reaching the end of the document, then calculate the frequency of a word.
+3. Repeat step 2 till the end of the document.
+4. Close document 1.
+5. Open document 2 and try to record data on it, and judge if it opens successfully at the same time.
+6. If open successfully, then record all the words and their frequencies in this document.
+7. Close document 2.
+8. Make all words fit in a static order (maybe from "a" to "z").
+9. Open document 3 and try to record data in it, and judge if it opens successfully at the same time.
+10. If open successfully, then record all the words and frequencies in the order in document 3.
+11. Close document 3.
+
+How to use loops:
+During the process calculating the frequency of one word.
+How to use advanced datatypes:
+Use structures to combine the words and their frequencies together.
+How to use functions:
+....
+How to use arrays:
+In the process of calculating the frequency of one word.
+Arrays:
+In the structure.
+
+External Library:
+I don't understand what is an external library, but I can find external help from my mom. She is a professor in Tsinghua University teaching computer linguistics.
+

reverse.c

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+#include <stdio.h>
+#include <string.h>
+
+int main(){
+	char string[20];
+	printf("Please enter a string within 20 characters:\n");
+	fgets(string,sizeof(string),stdin);
+	char* begin;
+	char* end;
+	char a;
+	begin=string;
+	end= begin + strlen(string)-1;
+
+	while(begin<end){
+		a=*end;
+		*end=*begin;
+		*begin=a;
+		begin++;
+		end--;
+	}
+
+	printf("%s",string);
+	return 0;
+}

strings.c

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+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+
+char* strcpy(char*s1,const char*s2){
+	assert((s1!=NULL)&&(s2!=NULL));
+	char*ret=s1;
+	while((*s1++==*s2++)!='\0');
+	return ret;
+}
+
+char* strcat(char*s1,const char*s2){
+	char* address=s1;
+	assert((s1!=NULL)&&(s2!=NULL));
+	while(*s1)
+	{
+		s1++;
+	}
+	while(*s1==*s2)
+	{
+		NULL;
+	}
+	return address;
+}
+
+int main(){
+	char* s1;
+	const char* s2;
+	printf("Please type in the first sentence:\n");
+	scanf("%s",&s1);
+	printf("Please type in the second sentence:\n");
+	scanf("%s",&s2);
+	printf("%s",strcpy(s1,s2));
+	printf("%s",strcat(s1,s2));
+	return 0;
+}
+
+
+